lang/rust: fix build on powerpc64 elfv2

After upgrade to LLVM 10, core in stage 1 fails to compile (no clear reason, rustc crashes):
pid 26828 (rustc), jid 0, uid 0: exited on signal 11 (core dumped)

Compilation with GCC works fine, so switch to GCC for the time being.

PR:		244813
Approved by:	mikael

lang/rust/Makefile

@@ -92,7 +92,7 @@ EXTRA_PATCHES+=	${PATCHDIR}/libgit2
 EXTRA_PATCHES+=	${PATCHDIR}/${ARCH}${BOOTSTRAPS_SUFFIX}
 .endif
 
-.if ${ARCH} == powerpc64 && ${PPC_ABI} == ELFv1
+.if ${ARCH} == powerpc64
 # The bootstrap is hardcoded to use gcc9
 # but we can build with a newer or older compiler as provided by USE_GCC=yes
 BUILD_DEPENDS+=	gcc9:lang/gcc9

lang/rust/files/powerpc64-elfv2/patch-src_bootstrap_native.rs

@@ -0,0 +1,13 @@
+--- src/bootstrap/native.rs.orig	2019-11-04 15:45:21 UTC
++++ src/bootstrap/native.rs
+@@ -241,6 +241,10 @@ impl Step for Llvm {
+             }
+         }
+ 
++        if target == "powerpc64-unknown-freebsd" {
++            cfg.define("CMAKE_EXE_LINKER_FLAGS", "-Wl,-rpath=/usr/local/lib/%CC% -L/usr/local/lib/%CC%");
++        }
++
+         // http://llvm.org/docs/HowToCrossCompileLLVM.html
+         if target != builder.config.build && !emscripten {
+             builder.ensure(Llvm {

lang/rust/files/powerpc64-elfv2/patch-src_librustc__llvm_build.rs

@@ -0,0 +1,18 @@
+--- src/librustc_llvm/build.rs.orig	2019-12-16 15:38:05 UTC
++++ src/librustc_llvm/build.rs
+@@ -273,7 +273,14 @@ fn main() {
+     };
+ 
+     // C++ runtime library
+-    if !target.contains("msvc") {
++    if target == "powerpc64-unknown-freebsd" {
++        if is_crossed {
++            println!("cargo:rustc-link-search=native=%WRKDIR%/usr/local/lib/%CC%");
++        } else {
++            println!("cargo:rustc-link-search=native=/usr/local/lib/%CC%");
++        }
++        println!("cargo:rustc-link-lib=static=stdc++");
++    } else if !target.contains("msvc") {
+         if let Some(s) = llvm_static_stdcpp {
+             assert!(!cxxflags.contains("stdlib=libc++"));
+             let path = PathBuf::from(s);